Intro to Fab. – Week 6

Working with Motors

So initially I played around with the idea of revisiting a couple projects from pcomp — a musical box that opened after the whole jeopardy theme song played (which had a motor held by a janky cardboard mount and an even more janky cardboard hinge) or my final pcomp project which was a motorized version of playing musical spoons using sad little servos.

Link

Instead, I decided to go a new / different route. I really like the mechanism of this example from class and wanted to use it in this assignment. Took a while to come up with an idea but I landed on building a magic 8 ball shaker, because why shake it with your hand when you can press a button and it will do it for you.

Honestly I have found this bit quite challenging and am still having some difficulties getting the right movement working.

Here are some bad sporadic sketches of trying to figure things out–

This has been tricky because with the magic 8 ball, the window poses a bit of an issue. At first, the movement I thought I needed kept the window horizontal, and the ball rotating on its center axis, which essentially kept the window flat and didn’t allow it to shake enough so that a new answer would appear. So I moved on to having it either twist on the x or z axis so that the window would move.

It was hard to visualize everything in my head so I made test cuts using cardboard and then test cuts with acrylic as well.

However, as I kept running into issues with making that piston action as well as the nuts and washers coming off of the screws as things rotated — dumb question but how do I keep them in place without tightening too much where nothing can rotate?

Anyways, because I kept running into issues with that mechanism and I knew more issues would come up like mounting it all, I decided to try using a DC motor instead of a tt motor. And because it spins so fast, I mounted the magic 8 ball straight on it in its mount and just had it spin on its center axis really fast, and luckily after it slows down when the button is released, the answers in the window do in fact change. I will keep this for my back up in case I really can’t get the other way to work for me in time.

Also, on the breadboard for the third video, I have two pairs of buttons that change the direction of the motor to help slow it down a little quicker — is this probably bad for the motor? Perhaps.

Here’s some testing footage–

LOCK NUTS — the answer to a good chunk of my problems. Was at Bruno’s this morning and saw them and didn’t know why I didn’t think of them. Then saw Ben’s example which uses lock nuts — so back on the somewhat right track.

Here’s test footage with the updated mechanism with lock nuts in place, as well as the double version, also — from Ben’s suggestion of only needing a single movement instead of using both sides of the motor, I tried to test out the motion with the 8 ball, it was a bit finicky because the suction base of the vise grip wouldn’t work, but I think once I mount the 8 ball as its intended to be — horizontally instead of vertically — to its housing/structure which will be made of wood I can do a better test (I’m also going to mount it on both ends so it’s not putting too much strain on the motor spindle) —

Cut out the magic 8 ball holder out of 1/8″ clear acrylic.

Started designing the actual mount for the motor and things, a tedious process with all of the tiny measurements but it’s come together. I made a test version with some wood and marked down some adjustments/additions that I need to make or forgot to include.

So originally, I was using the axis of the DC motor as a means for the 8 ball to rotate, with the intention of having the DC motor as a backup if I couldn’t get the tt motor mechanism working in time. However, it was hard to find out the correct screw size for mounting the DC motor — wasn’t an M2, or a #2-56 or #4-40 — so after looking at different screw size charts both metric and imperial and looking on metric screw kits on Amazon, I made a guess and ordered M2.5 screws — how annoying.

Side note — on my hunt to find out what the screw size was, I came across a lovely Amazon q and a pictured below.

But before those got delivered, Ben and I figured it’d be less painful to just use a metal rod. Thankfully he had some 1/4″ flanged couplers and I had 1/4″ aluminum rods. Although, the aluminum rods didn’t quite work but luckily I had 1/4″ wooden dowels that were a tad smaller so they were able to slot into the couplers.

Once I recut parts of the 8 ball mount to accommodate the new couplers, I worked on figuring out the structure that everything will be mounted to. I measured out at what height I wanted the 8 ball suspended at, stacked two 1×4 pieces of wood and used the drill press to make 1/4″ holes so that the 8 ball / rods would be level.

UPDATE: The screw size for the DC motors is in fact M2.5. Annoying.

In terms of the base, I drilled a 1″ hole roughly 3/4 of the way into the base and then a (I think) 7/8″ hole perpendicular to the 1″ hole for some wiring. This is where the motor will be mounted.

Next, I cut out the entire mount for the motor out of acrylic. After a stupid amount of resizing the slot for the motor’s spindle, finally had it right. Honestly assembling it all was a real pain in my ass.

After about 20 years, I finally had it all pieced together correctly and was able to start testing the entire motion of everything and find tuning some adjustments.

Now what’s left to do is assemble everything to the base and get the wiring all sorted out. I was able to squeeze some corner brackets to the bottom of the motor mount which will help hold it in place to the base.

Assembled and glued the structure together. The push-arm is a bit finicky — I think part of it gets a bit stuck sliding up and down. I’ll try and address it again.